Summary - Embedded C

Combine MMIO, interrupts and bit manipulation to write an LED blink app.

Summary - LED blink app

In this lesson you'll combine MMIO, interrupts and bit manipulation to write an LED blink app. The program toggles a fake GPIO register in a loop, printing the LED state each step.

The register is volatile (MMIO). Inside the loop, ^= does the bit toggle (bit manipulation). Each iteration prints the state; this is like monitoring interrupt activity. Three iterations: LED turns on, then off, then on again. This exercise combines the core patterns of embedded C in one program.

Exercise Write an LED blink program

Define static volatile unsigned int gpio = 0; (fake GPIO register). In int main(void) write for (int i = 0; i < 3; i++). Inside the loop toggle the LED with gpio ^= (1 << 0); and print the state with printf("LED: %d\n", gpio & 1).

Show example solution

#include <stdio.h>

static volatile unsigned int gpio = 0;

int main(void) {
    for (int i = 0; i < 3; i++) {
        gpio ^= (1 << 0);
        printf("LED: %d\n", gpio & 1);
    }
    return 0;
}

Test yourself

Which operation is used for LED toggle?
- |=
- ^=
- &=
- =
Show answer

^= — ^= toggles the bit; it fits LED toggle.

Complete the toggle operation

gpio ^= (1 << ____);  /* LED'i değiştir */

Show answer

gpio ^= (1 << 0);  /* LED'i değiştir */

Match embedded concept to role

MMIO

Hardware access
volatile

Prevent optimization
Toggle

Flip with ^=
Loop

Keep running

Next lesson: Project design

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